View Full Version : Engine identification ?

09-29-2017, 10:30 AM
Just hauled in 3 Cj's . a 51, a 48, & a 46...
on the 51 CJ3, the engine in it now, has what appears to be the casting # on the lower right side of the block, 641087-L-W10-A-NA. Add:
The Head says " Kaiser -Super Sonic" on it also..
Can you guys help me to indentify what this is ?
Thanks in advance

01-17-2018, 02:16 AM
maybe you can see this?http://www.cj3apage.com/index/Tech_Tips/casting%20numbers.htm

51 CJ3
01-17-2018, 07:14 AM
Try this https://www.thecj2apage.com/forums/kaiser-supersonic-head_topic21379.html

51 CJ3
01-17-2018, 07:17 AM
Wow, my last post had to go through a moderator. I haven’t seen that before. It was a link to another forum that I found on google by searching for “Kaiser supersonic head”.

01-17-2018, 12:12 PM
Unless someone swapped it, the '51 CJ-3 should have the L-head 134 engine (the flathead engine). Kaiser and Willys were interchangeable back then, and a lot of one fit the other - with just minor differences in marking.

While there may have been minor differences between Kaiser Supersonic and Willys Overland originally - at this late date they are the same.

You probably have a garden variety L-134 that someone swapped the head - or Willys borrowed parts from the other side of the house one week in 1951. Not at all unusual back then.

01-17-2018, 01:57 PM
I'm not sure on how much truth there was to it, but I read somewhere (ewillys) that the Kaiser Supersonic heads were thought of a performance enhancer. The compression may be a bit higher, but I haven't noticed any difference in my 46 CJ2A. The Super sonic head was on there long before we bought it, but compared to other Willys L134, they act about the same.

51 CJ3
01-18-2018, 07:18 AM
My censored link mentioned an extra 5 hp and it was suggested it would have come from one of the Kaiser cars.

01-18-2018, 07:35 PM
AS you look through the really old stuff, Kaiser allegedly had different heads - like high altitude heads and such. Supposedly, they were originally painted different colors - but the more suspicious of us believe that the biggest difference was the paint.

As far as a 5 HP boost with a Kaiser Supersonic head, the total redesign of the L-134 to the F-134 only gave about 10 HP improvement. I doubt that a different head would make that much difference.

Most old L-134's got that boost after about 5 or 10 years when you had to plane the head to cure the warp after a blown head gasket. If the engine was rebuilt, it was not unusual for the engine serial number on the water pump boss to get removed when the top of the block got cleaned up as well. Good shops would restamp the number elsewhere on the block so it wasn't lost.

51 CJ3
01-18-2018, 08:44 PM
One of the posts I was reading claimed they had a supersonic head laying next to a regular head and they were different. It was suggested the supersonic head allowed for a higher compression ratio. I’m not an engine guy but I know increasing the compression ratio from 7:1 to 8.5:1 on a Lycoming O-320 is good for an extra 10 hp (published data easy to verify).

51 CJ3
01-22-2018, 12:07 AM
Okay, it took a little digging but, if I am tracking all of the sources that led me to my destination correctly, the supersonic should be worth about 8 extra hp according to Wikipedia. They have the Henry J engine listed at 68 as compared to the Go Devil at 60 hp. Both are L134. Both came from Willys. Unfortunately, Wikipedia isn’t always the most reliable source of information but they usually have references to back what is posted.

01-22-2018, 07:38 AM
It would be fun to take the engine in my 46, with the Kaiser super sonic head, and run it on the engine dyno, then swap to a conventional Willys head. I'll put that on the bucket list for when I win the lottery.

51 CJ3
01-22-2018, 11:42 AM
Dyno info would be great but pictures of the heads side by side would be good too. Not a lot of easy to grab information on the engines outside of forum rumors. I saw somewhere the Supersonic engine was good for 7.3:1 or 7.5:1 compression but I haven’t been able to find it again. Wikipedia shows the Go Devil as being 6.48:1 but my maintenance manual lists 7:1. Maybe the year makes a difference. I don’t think compression by itself is enough for the boost in HP but combined with one or two other mods it may. The heads and other parts are said to be interchangeable between the engines (Wikipedia). One forum participant said Sears also sold the Supersonic as a replacement engine for the Jeeps so, in addition to the possibility this engine and/or head was swapped with parts from a Kaiser car, we also have the possibility it came from Sears as a replacement for the original Jeep engine.

01-22-2018, 03:19 PM
I have seen an All State replacement engine once. It was in a Hobart welder.

I don't have real good pictures of the Super Sonic head on my 46, and could not find a clear picture on line. The third picture was the best I could come up with. The last two pictures are of a standard Willys head. There should be some pictures out there somewhere of both heads side by side. I'll keep on the lookout.

51 CJ3
01-22-2018, 09:45 PM
I haven’t been able to find any more on the engines. Not even references to the different heads LarrBeard mentioned. It stands to reason the Supersonic engine just used a shaved down Go Devil head. I may have to go to the library on the next rainy day and do some “old school” research.

01-23-2018, 12:51 PM
Check that they rate HP at the same RPM and at what torque...

In a Henry J, the rear axle ratios would have been a lot different that in the CJ's so that gave a bit of room on specsmanship. After all - 1n 1950 or so, you would expect your family car to have a lot more horsepower that that old Jeep you drove through Belgium!

51 CJ3
01-23-2018, 08:35 PM
Did the early Go Devils have less power? I keep coming across a 6.48:1 compression ratio reference. The jeep service manual I have claims 7:1. The Henry J references I have seen all say it is the same engine as used in the CJ3A with minor changes so parts were interchangable. I haven’t found anything stating the rpm used to get 68 hp. If they compared engines with the above compression ratios there would have been more hp but I don’t think 5 hp, let alone 8.

01-24-2018, 06:06 AM
Initial power output for the Go Devil was 60 hp at 4000 rpm and 105 lb⋅ft of torque at 2000 rpm with 6.48:1 compression. The 7:1 ratio was for high altitude models, meaning that the horsepower would have been the same at 10,000 elevation, as it was at sea level. That's why you don't see horse power ratings with the Super Sonic heads installed.

The following link has a lot of information on the Go Devil. Some of your questions are answered within.

51 CJ3
01-24-2018, 08:33 AM
That’s a good link, thanks for posting it. It contains more information than I had come up with across a dozen websites in just one article. It’s no wonder there are varying hp claims. According to this article they are all true at 4000 rpm.

51 CJ3
01-24-2018, 09:53 AM
I'm not sure on how much truth there was to it, but I read somewhere (ewillys) that the Kaiser Supersonic heads were thought of a performance enhancer. The compression may be a bit higher, but I haven't noticed any difference in my 46 CJ2A. The Super sonic head was on there long before we bought it, but compared to other Willys L134, they act about the same.

The hp rating is made at 4000 rpm. I can’t imagine spinning one of these engines that fast very often. The difference at lower rpm would be less and could become nonexistent when combined with other variables.

It would have been nice if Willys or Kaiser had published some information about different heads available. I just had another look at the maintenance manual and so far all I see is a 7:1 compression ratio listed. My parts manual lists 2 part numbers. The first one listed is for the 6.48 head. The second one has a part number lower in sequence and says “(up to engine serial no......)” which leads me to believe it was an earlier head. My parts manual is from Willys-Overland. My service manual is from Kaiser. I wonder if a Kaiser parts manual may have more information.

01-24-2018, 02:07 PM
Take the two manuals and bounce the information against the military M38 Technical manual. This should be the most complete information in regards to the latter Go Devil engine.


51 CJ3
01-26-2018, 02:06 PM
The military did what the military does...just caused more confusion. According to the military manuals the MB and GPW engine put out 54 HP at 4000 rpm and the M38 engine put out 51 at 4000 rpm. Both claimed 6.48:1 compression ratio. I did find 2 different manufacturer part numbers for cylinder heads in those books. I like the numbers in the CJ books better.

51 CJ3
01-26-2018, 10:07 PM
I have been learning a lot the last few days while researching the heads. Not hard since I didn't know much to start with but one of the surprises was finding the CJ3A listed as a military vehicle 2 pages after the MB and the page before the M38 and again on the very next page (TM 9-2800-1 pages 151-155). It is the only "CJ" specifically called out in that manual (1953).

02-05-2018, 09:03 AM
Here is a listing for a duel carb set up for the Willys L head. Performance parts are out there, but few and far between.


51 CJ3
02-05-2018, 10:17 AM
That’s cool. And very tempting to bid on.

02-11-2018, 08:32 PM
just bought a 53 m38-a1 has kaiser willys supersonic 4l134 engine with L head is this correct engine for the m38a1

02-12-2018, 06:33 AM
The correct engine for the M38A1 is the 134 F head.

M38 engine;

M38A1 engine;